Serotonergic involvement in the psychosocial dimension of personality

Neurotransmitter systems have been associated with aspects of personality and changes in various dimensions have been shown after antidepressant treatment. A reduction in harm avoidance and an increase in self-directedness and cooperativeness, as measured by the Cloninger's Temperament and Character Inventory (TCI), have been reported in psychiatric patients receiving treatment with serotonergic antidepressants. However, some of these changes have been associated with clinical improvement. The present study therefore used a randomized, double-blind, placebo-controlled design to examine the role of the serotonergic system on these personality factors in the normal population. Twenty healthy male volunteers were randomly allocated to either placebo (n = 9) or citalopram treatment (n = 11) for 2 weeks. Baseline depression and anxiety scores were low and did not differ between groups. The TCI was administered pre- and post-treatment. There were no baseline differences on any TCI factor between groups. Citalopram induced a significant increase in self-directedness (p < 0.05) but not cooperativeness or harm avoidance ratings after treatment. Thus, citalopram has effects on personality aspects which appear to be separate from its antidepressant properties.